To translate Windhawk, pick one of the YAML files (for example, en.yml for English), and translate the text on the right side of the colon.
For example, here's an excerpt from the English translation file:
app:
appHeader:
home: "Home"
explore: "Explore"
settings: "Settings"
about: "About"
In this excerpt, the "Home", "Explore", "Settings", and "About" are the strings that need to be translated.
If you're familiar with GitHub, you can contribute a translation by submitting a pull request.
If you're not familiar with GitHub, you can download the translation files, translate one of the files, and send it via email.